The long range objective of this proposal is to study the regulation of glucose production (glycogenolysis and gluconeogenesis) both in vivo, using the conscious and anesthetized dog, and in vitro using isolated dog hepatocytes and perfused rat liver. Gluconeogenesis will be studied by determining the hepatic and renal uptake of gluconeogenic precursors and by quantitating their conversion into glucose. Overall glucose production will be measured using A-V difference and tracer (3H-3-glucose) techniques. These measurements will be made possible by surgical implantation of catheters for blood sampling in the portal, hepatic and renal veins and femoral artery two weeks prior to study. Clear interpretation of data will be possible because both the pancreatic hormone levels and the plasma glucose concentrations will be controlled and in accordance with the need of an experiment. Regulation of insulin and glucagon secretion will be achieved surgically or pharmacologically by inhibiting the animal's pancreatic hormone secretion and quantitatively replacing both insulin and glucagon intraportally. The surgical approach involves a "pancreatic autograft" technique and the pharmacological approach involves infusion of somatostatin (a potent inhibitor of insulin and glucagon secretion) coincident with pancreatic hormone replacement. Glucose will be regulated using a glucose-clamp technique. Studies will be carried out in vitro using isolated dog liver cells to study the mechanisms by which certain changes observed in vivo occur. Utilizing the above methods our main objectives will be to examine 1) the physiologic importance of the catecholamines in regulating glycogenolysis and gluconeogenesis in vivo; 2) the interaction between insulin and epinephrine in regulating these processes; 3) the interaction between cortisol and epinephrine in regulating these processes; 4) the role of glucagon in regulating glucose production in the fasting state; 5) the role of glucagon in regulating post-feeding lactate production and 6) the mechanism by which the effect of glucagon is turned off inside the liver cell.